Scope of Whole Genome Duplication in Forages: A Plant Breeder Perspective

Abstract

Polyploidy is a condition of having more than two sets of chromosomes. Polyploid plants may be artificially obtained through chemical, physical and biological methods (2n gametes). It is considered an interesting approach due to increased genescope and expression, thus resulting in phenotypic changes, such as yield and product quality. Nonetheless, breeding new cultivars through induced polyploidy should overcome deleterious effects partly contributed by genome and epigenome instability after polyploidization. Furthermore, shortening the time required from early chromosome set doubling to the final selection of high yielding superior polyploids is a must. Despite these hurdles, plant breeders have successfully obtained polyploid bred-germplasm in broad range of forages from optimized application methods, concentration and time mainly using colchicine. These experimental polyploids proved to be a valuable tool for understanding gene expression that is driven by dosage dependent gene expression, altered gene regulation and epigenetic changes. Isozymes and DNA-based markers aided on the identification of rare alleles for particular loci when compared with diploids, which may explain their heterozygosity, phenotypic plasticity and adaptability to diverse environments. It has also been observed that experimentally induced polyploid germplasm could enhance fresh herbage yield and quality, e.g. leaf protein content, leaf total soluble solids, water soluble carbohydrates and sucrose content. Offspring of experimentally obtained hybrids underwent selection for several generations to improve their performance and stability.